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Fixed gas detectors

A fixed gas detector is a gas sensor used to monitor concentrations. There are different types of gas transmitters like combustible gas transmitters (natural gas, LGP, hydrocarbons, solvents, alcohols), toxic gas monitoring systems, VOC meters (volatile organic compounds), asphyxiant gas or refrigerant monitoring systems (for freons).

Fixed gas detector or gas transmitter in complete fixed gas detection systems

Most of fixed gas detection systems for toxic and combustible gases feature a 4-20 mA linear output to connect to a gas detection controller and areATEX compliant. A more advanced fixed gas detector can also be equipped with a digital display, alarm relays or digital communication. There is a specific sensor technology for each type of gas that ensures the accuracy and the frequency of measurements… (Learn more about sensor technologies).


    A combustible gas detector (natural gas, LPG, hydrocarbons, solvents, alcohols) stands for the largest part of gas detection. A fixed gas detector for combustible gas can be used in almost any sector: industries with SEVESO  or COMAH sites, chemistry, petro chemistry and also in the tertiary sector with boiler rooms gas detection for example. There are two major monitoring technologies depending on the targeted combustible gas to detect :

    . Catalytic sensors: sensor technology used for almost every combustible gas. This solution is very efficient for natural gas, LPG, hydrocarbons, solvents and even some volatile compounds monitoring.

    . Infrared sensors: this technology should be preferred for every sector with a constant residual presence of combustible gases (refineries, paint or solvents plants, distilleries…).


    As the use and the manufacturing of highly toxic products in the industry is growing stronger, dangers to goods (risk of explosion) and to people (risk of poisoning) are growing as well. Throughout the world every day explosions and death occur and recall this problem.

    The most commonly used sensor technology for monitoring toxic gases is the electrochemical sensor. This technology, that can be found in a portable or a fixed gas detector, provides a large panel of gas detection sensors. For some rare gases that require measurements expressed in ppb (parts per billion), only the colorimetric paper technology will be available for fixed gas detection.


    Asphyxiating gases includes many gases with the same property: they reduce oxygen rate. Even if in almost any case an oxygen gas detector (O2 detector) is enough, it is recommended to use an asphyxiant gas detector when it is available such as a CO2 gas detector (carbon dioxide) or an helium fixed gas detector for example.

    . Electrochemical sensor for oxygen and some rare gases

    . Infrared absorption sensor for carbon dioxide (CO2)

    . Catalytic sensor for almost any combustible gas that can replace oxygen in case of leakage


    Volatile organic compounds (VOC) are a wide family of gases and gaseous substances that can be pollutant, toxic and even carcinogenic. As they are volatile, they can easily spread into the atmosphere. That’s why it is necessary to detect and measure them with a fixed VOC monitor to be protected.

    Even if VOC can compose explosive mixtures, they are very toxic before their concentrations reach an explosive level (tens of thousands parts per million). Indeed, their level of explosiveness is set at tens of ppm. Several technologies for VOC detectors are available depending on the risk to monitor:

    . Photo-ionization lamp (PID lamp) or semi-conductor sensor for toxicity detection (expressed in ppm).

    . Catalytic sensor or infrared absorption sensor (when available) for explosiveness detection (expressed in % LEL).


    Halogenated hydrocarbons (CFCs and HCFCs), alkenes (HFOs) and almost any refrigerant gas are regulated under a particular legislation that limits (or forbids) their use. The use if refrigerants also requires a monitoring system – usually a fixed gas detector for freons. There are two main measuring technologies for freons:

    . Semi-conductor sensors: the most commonly used technology for freons monitoring

    . Infrared absorption sensors: a very accurate but very expensive technology used for some freons

GazDetect offers, on specific territories, many services for fixed gas detection like on-site installation, setup, commissioning and calibration of gas detectors. We can also perform maintenance and periodical checkings of your fixed systems. (go to the Maintenance and on-site calibration section)

Our fixed gas detector range :

Fixed H2S detector – semiconductor technology – OLCT710 TP

The OLCT710 TP is a fixed gas detector dedicated to hydrogen sulfide monitoring. This H2S gas transmitter was especially designed to be efficient in high H2S concentrations and is ideal for use in oil and gas applications, or water & wastewater treatment plant environments

  • Fixed H2S detector with semiconductor gas sensor OLCT710 TP by Oldham
  • Semiconductor gas sensor technology
  • ATEX & SIL2 certification
  • Made for use even in the harshest conditions (-40°C to +75°C)
  • IP66 protection ingress
  • 4-20 mA analog output & RS48 Modbus
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Fixed VOC detector XDI PID

Used in a complete gas detection system or as a stand alone monitor, the VOC detector XDI-PID is dedicated to  volatile organic compounds monitoring. This fixed detector with a photoionization lamp is an ATEX certified transmitter, with a 4-20 mA linear output, a digital display and alarm relays.

  • VOC monitor, volatile organic compounds fixed detector with PID lamp
  • ATEX VOC detector
  • 4-20 mA output + 3 configurable alarm relays (alarms and/or fault)
  • Humidity-resistant (no compensation needed)
  • Solid and resistant device for the most demanding environments
  • Large optional backlit LCD display
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Especially designed for the detection of oxygen, combustible and toxic gases, the OLCT10N digital fixed gas detector ensures reliable and fast concentration levels monitoring. Every information is sent to the gas detection controller in less than a second.

  • Fixed gas detector OLCT10N
  • Detection of CH4, O2, CO, H2S, NO, NO2, NH3.
  • Power supply 12-30 V DC.
  • RS485 Modbus digital signal.
  • Immune to dust and water.
  • ATEX 3 GD, ATEX 2 and 22 approved.
  • Additional information
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With its infrared technology the GD10P fixed gas detector monitors hydrocarbon vapors and CO2 carbon dioxide. The detector's auto-test function signals defaults on the optical system or malfunction to the controller and requires minimal maintenance.

  • Détecteur gaz fixe avec technologie infrarouge - GD10P
  • Fixed gas detector with infrared technology: hydrocarbons vapors and CO monitoring
  • 5 years guarentee – 15 years warranty on the infrared sensor (Simtronics patent)
  • Ongoing auto-test: signals optical defaults or malfunction to the controller
  • No saturation: the detector is able to monitor concentrations up to 100% vol.
  • Factory calibration, no onsite calibration, minimal maintenance
  • Additional information
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Gas detector – refrigerant gas leak – OLCT10 Freon

OLCT10-Freons refrigerant gas leak detector with 4-20 mA linear output for refrigerant application in classified area.

  • Fixed gas detector OLCT10
  • Detection of R11, R12, R22, R23, R32, R123, R134A, R141B, R143A, R227, R404A, R410A, R407C, R408A, R507, FX56
  • Power supply: 15 to 30 VDC – 4-20 mA linear output
  • Robust, compact and easy to use
  • Approval: ATEX II 3 G / EEx nA IIC T4 – Electromagnetic compatibility according to EN-50270
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SIL 2 approved ATEX gas detector to detect the combustible gases (IR or catalytic), CO2 (IR), toxic gases (electrochemical), solvents or freons (semiconductor) and asphyxiating gases (oxygen deficiency).

  • Fixed gas detector OLCT100
  • Detection of hydrocarbons, solvents, toxic gases, freons, VOC, CO2
  • Housing made of aluminium with epoxy paint (optional 316L Stainless Steel version)
  • Outputs: OLC100: Wheatstone bridge – OLCT100: 4-20 mA linear
  • Power supply: 15.5 to 32 VDC
  • ATEX & SIL 2 approved for catalytic and infrared versions
  • Additional information
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Gas detector – OLCT10 Atex

Especially designed for use in boiler rooms or parkings, the OLCT10 sensor range is used to monitor presence of explosive vapors and gases or combustion toxic gases in ambient air.


  • Fixed gas detector OLCT10
  • Detection of the combustible gases, CO, NO, NO2
  • Power supply: 15 to 30 VDC
  • 4-20 mA linear output
  • Robust, user-friendly and easy to install
  • ATEX II 3 G / EEx nA IIC T4 approved
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Fixed gas detector SERIE 3000 for oxygen and toxic gas

Loop-powered (4-20 mA 2 wires) and equipped with an LCD display, the Serie 3000 fixed oxygen and toxic gas detector is particularly well-suited for potentially explosive atmospheres (ATEX zones).

  • Fixed gas detector serie 3000 transmitter
  • Large range of pre-calibrated gas detection sensors
  • Loop-powered, 2 cables
  • LCD screen for setup and concentrations display
  • Aluminum version or stainless steel with epoxy paint version
  • Approved for hazardous areas, L/c-UL, ATEX, IECEx. Protection IP66 (EN 60529), NEMA 4X
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Gas detector with display – XCD ATEX

ATEX gas detector with 4-20 mA linear output, display, 3 relays (alarm 1, alarm 2 and fault) and MODBUS communication. Detection of the combustible gases (IR or catalytic), CO2 (IR) or toxic gases (electrochemical).

  • Fixed gas detector XCD
  • Detection of combustible gases, CO, CO2, CH4, H2, H2S, O2
  • Power supply: 15.5 to 32 VDC with 4-20 mA relay output
  • Aluminium or IP 65 stainless steel housing
  • Approval: ATEX II 2G EExd ia d IIC T4
  • Integrated mounting plate with 3 mounting holes – 2 M20 cable gland entries
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4-20 mA detector/transmitter with relay outputs and RS485 communication. Pre-calibrated sensors to detect oxygen, flammable and toxic gases.

  • Fixed gas detector OLCT80
  • Detection of O2, CO, CO/H2 NUL, H2S, NO, NO2, SO2, Cl2, H2, HCl, HCN, HF, NH3, ETO, O3, PH3, ClO2, SiH4, COCl2, AsH3, CH4, H2, NH3, VOC
  • Alarms: 2 gas alarms (alarm 1, alarm 2) and 1 fault alarm
  • Inputs and outputs: 4-20 mA with signal smart treatment
  • Approval: ATEX – II 2 GD, INERIS 03ATEX0240X, compliance with EN50270 standard, IP66
  • Additional information
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Infrared (IR) combustible gas and hydrocarbon detector with 4-20 mA output. ATEX and SIL 2 (EN 50402) approved with many factory configured calibration curbs.

  • Fixed gas detector Optima +
  • Detection of the combustible gases
  • More than 40 specific gas curbs available factory calibrated
  • 4 ray dual source infrared IR technology
  • Very fast response time (T90 < 8 seconds)
  • Very high reliability (MTBF > 28 years)
  • Additional information
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Toxic corrosive & combustible gas detector – satellite xt

The Satellite XT is a fixed gas detector with interchangeable sensors. It is especially designed to continuously monitor hazardous concentrations of gases.

Detected gases: AsH3, BBr3, B2H6, BCl3, BF3, Br2, C2H4O, Cl2, ClF3, ClO2, CO, COCl2, F2, GeH4, H2, H2S, H2Se, HBr, HCl, HCN, HF, HMDS, MCF, MMH, N2H4, NH3, NO, NO2, O2, O3, PH3, POCl3, SiCl4, SiHCl3, SO2,TBA, TBP, TDMAT, TEOS, TMB, TMP, UDMH, WF6.

  • Fxed gas detector Satellite XT
  • Pyrolysis module detection: C4F6, C5F8, CH3F, DCE 1.2, NF3, SF6
  • Pre-calibrated interchangeable sensors, easy maintenance
  • 4-20mA linear output
  • 3 optional single-pole relays
  • Optional remote measure (up to 3 meters)
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4-20 mA gas detector / transmitter with integrated sampling pump, pre-calibrated cartridge, alarm relays and TCP/IP communication.

Detection of AsH3, B2H6, BCl3, BF3, Br2, C2H4O, Cl2, ClF3, ClO2, CO, COCl2, F2, GeH4, H2, H2S, H2Se, HBr, HCl, HCN, HF, HMDS, N2H4, NH3, NO, NO2, O2, O3, PH3, POCl3, Si2H6, SiCl4, SiHCl3, SO2, TEOS, TMB, TMP, WF6

  • Fixed gas detector Midas
  • Detection with pyrolysis module of C4F6, C5H8, CH3F, DCE 1.2, NF3, SF6
  • Integrated aspirated pump: 500 mL/min flow
  • 3 configurable NO or NF alarm relays
  • High accuracy measurement from ppb to ppm
  • Ethernet (PoE) TCP/IP and Modbus communication
  • Additional information
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B12 2 wire transmitter with 4-20 mA output for use in environments with up to 100% relative humidity.

  • Fixed gas detector B12
  • Power supply: from 12 to 28 VDC – low consumption
  • Measuring range: 0-10/100 ppm or 0-200/2,000 ppm
  • Corrosion-resistant sensor
  • Direct real-time measure of H2O2 concentration
  • Operating temperature: between 0 and 50°C
  • Additional information
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Toxic gas optical analysis – SPM FLEX gas detector

The SPM Flex is an optical calibration-free gas optical analysis system. This single point tape-based toxic gas detector can accurately (ppb measurement) and swiftly monitor the presence of a hazardous gas.

  • Honeywell SPM Flex gas monitor with optical toxic gas analysis
  • Chemcassette® technology – immune to interferences, more than 50 available gases.
  • Calibration-free, minimal maintenance .
  • Audiovisual alarm (2 thresholds).
  • User-friendly interface and gas concentration digital display.
  • UL 61010-1 / CSA-C22.2 / IEC 61010-1 certified

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Volatile organic compounds detector – TVOC

The TVOC is a VOC (volatile organic compounds) detector with stationary photoionization for continuous accurate measurements.

  • Détecteur de COV (composés organiques volatils) TVOC
  • PID sensor: 10.6 eV lamp and Ion Science technology
  • Power supply: 5 to 23 VDC and 4-20 mA or IS 8 – 30 VDC output
  • 4 digit LCD display, 4 alarm colored LED
  • Measuring range: from 0 to 100 ppm and from 100 to 1,000 ppm
  • ATEX approved for use in hazardous areas
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